Gramophone-tone-arm joint



Feb. 17, 1931.

A. F. J. WRIGHT GRAMOPHONE TONE ARM JOINT Filed May 26, 1 928 Patented Feb. 17, 1931 UNITED star ALBERT rnnnnnrcx JAMES weren't, on wnnrnniusrow, ENGLAND GRAMOPHONEPTQNE-ARM JOINT Application filed May so, 1928, Serial No. seas-r1, and in Great Britain August 27, 1927.

This invention relates to gramophones and like sound reproducing machines, and is particularly concerned with the joint between the tone arm of such a machine and the sound box.

It has already been realized as desirable to employ a joint with sound insulating properties between the two, and this object has been sought to be attained by inserting a sleeve of india-rubber in the joint.

In accordance with the invention, the sound box is provided with a tubular extension within which is inserted the end of the tone arm, while between the two there is a sleeve of indie-rubber or like material, and the arrangement is such that the sleeve, when subjected to axial pressure by means of a union nut, bulges so as to come into contact firmly with the tubular extension on its outer surface'and with the tone arm on its inner surface; this bulging, in fact, forms the oint between the tone arm and the sound box. In this way a simple form of joint is provided wherein there is no metallic connection between the tone arm and the sound box, and an india-rubber sleeve in fact forms the only connection. Furthermore, the amount of ax ial pressure produced by the union nut is perfectly adjustable with the result that the flexibility of the resulting joint between the tone arm and the sound box may be controlled as desired. Also this arrangement allows the joint to adapt itself to tone arms of somewhat dififerent diameters such as are always met with in practice.

A form of construction in accordance with the invention showing the joint between the tone arm and the sound box isillustrated in the accompanying drawing, which is a central section through the parts.

The casing a of the sound box is formed with a rearward tubular extension I) screw-v The tone arm shown in chain lines at 0 extends into the threaded on its outer surface.

tubular extension I), and its end is shown abutting against an india-rubber ring d. The sleeve 6 of india-rubber is inserted between the tubular extension 7) and the tone arm 0, but when this sleeve has its normal or initial shape, it does not make a tight joint.

The sleeve, however, isarrangedso that it can be longitudinally pressed by means of the union nut 7 which bears on the end of the sleeve 6 through a thin metal ring 9. The result of tightening up the nut f is that the sleeve 6 is pressed axially or longitudinally and tends to bulge outwards at its middle portion, where it thus comes into contact firmly with the tubular extension 7), whereas its inner surface at or near its ends is brought firmly into contact with the tone arm 0.

It will be noted that there is no direct metallic Contact between the sound box a and the tone. arm 0, while the joint is ex tremely simple and can readily be taken to pieces or re-assembled. Moreover, it has been found in actual practice that the quality of the reproduction is considerably improved by means of the novel joint.

1. In a sound reproducing machine having a tone arm and a sound box with a tubular extension from same, the combination of a sleeve of elastic material, having an axial length substantially greater than the thick- 7 ness of its wall, said sleeve surrounding the end of said tone arm and housed within said tubular extension, and means for exerting axial pressure on said sleeve to deform the same into contact with said tone arm and tubular extension.

2. In a sound reproducing machine having a tone arm and a sound box in combination, a tubular extension from said sound box, a sleeve of relatively flexible and elastic material housed Within said tubular extension, a

' plain cylindrical end to said tone arm initially retractably housed within said sleeve and means forexerting axial pressure in said sleeve to deform the same into contact with said tone arm and said tubular extension.

3. In a sound reproducing machine having a tone arm and a sound box in combination, a tubular extension from said sound box, a sleeve of relatively flexible and elastic material housed within said tubular extension, a plain cylindrical end to said tone arm initially retractably housed within said sleeve and a member having screw threaded connection with said tubular extension and shaped to press upon said sleeve to deform the same into tight contact with said tone arm and said tubular extension.

4. In a sound reproducing machine having a tone arm and a sound box in combination, a tubular extension from said sound box, a sleeve of relatively flexible and elastic material housed Within said tubular extension, a plain cylindrical end to said tone arm initially retractably housed Within said sleeve, a memher having screw threaded connection with said tubular extension and shaped to press upon said sleeve to deform the same into tight contact With said tone arm and said tubular extension and an india rubber ring inserted between said sound box and the end of said tone arm.

In Witness whereof I hereunto subscribe my name this 17th day of May, 1928.

ALBERT FREDERICK JAMES WRIGHT. 

